README

Loose TS check

The loose-ts-check utility helps ignore particular types of TS error in specified files.

This is useful when migrating to a stricter tsconfig.json configuration incrementally, where only some existing files are allowed to have TS errors.

Features

ignores specific TS errors from specific files
detects files that no longer have to be loosely type-checked
auto-updates the loosely type-checked list of files when a file no longer has error
auto-updates the ignored error codes when there are no errors of that type

Why not `exclude` in `tsconfig.json`

The exclude option in tsconfig.json only tells tsc to not start type-checking from those files. If some already type-checked file imports a file listed in the exclude, it will still be type-checked.

Thus, it does not suit this use case.

Why not follow the idea from the VSCode project

The vscode team have already encountered a similar problem and solved it in another way. They created a new tsconfig.json that only included some files.

While this works great with existing files, it does not automatically enforce a stricter config for new files in the project.

Installation

Install the utility with:

npm install loose-ts-check --save-dev

Usage

Pipe the result of tsc to loose-ts-check to run the utility:

tsc --noEmit -p tsconfig.strict.json | npx loose-ts-check

To initialize the list of ignored errors and loosely type-checked files based on the current errors, run:

tsc --noEmit -p tsconfig.strict.json | npx loose-ts-check --init

To automatically update the list of loosely type-checked files, run:

tsc --noEmit -p tsconfig.strict.json | npx loose-ts-check --auto-update

Options

Display the list of options by running:

npx loose-ts-check --help

Recipes

Reusing the same tsc output

To avoid running tsc again and again when testing, save the output to a file:

tsc > errors.log;

And then, use the tool by redirecting the input:

npx loose-ts-check < errors.log

Migrating to a stricter tsconfig.json

To migrate the codebase to use a stricter tsconfig.json, you will need 2 tsconfigs:

tsconfig.json - the strict tsconfig. This config will be used by the IDE and by the loose-ts-check tool.

The aim is to see the errors in the IDE, to feel motivated to fix the errors while modifying existing files.
tsconfig.loose.json - a tsconfig that extends tsconfig.json, but has the stricter options turned off.

This config will be used by any linter, test runner, bundler you will have.

If you are using ts-node, you need to pass tsconfig.loose.json as a TS_NODE_PROJECT variable, so it uses the correct tsconfig, e.g.
```
cross-env TS_NODE_PROJECT="tsconfig.loose.json" webpack --mode=development
```
To run tsc to do type-checking, pass -p tsconfig.loose.json option:
```
tsc -p tsconfig.loose.json
```

Then, use the following command to initialize the config files:

tsc | npx loose-ts-check --init

After that, run

tsc | npx loose-ts-check

instead of tsc to do type-checking.

Development

To verify the correctness, run:

npm run type-check
npm run lint:formatting
npm run test

Contributing

Contributions are welcome!

Make sure the CI passes on your PRs, and that your code is covered by unit tests.

Usage no npm install needed!